Radio frequency identification (RFID) is a technology used for unique identification of a target, e.g. an object, animal, or person. RFID technology incorporates the use of electromagnetic or electrostatic coupling in the radio frequency portion of the electromagnetic spectrum. Radio frequency identification is coming into increasing use in industry as an alternative to the commonly used bar code. Bar codes require direct contact or line-of-sight when scanning, whereas the radio frequency identification can be verified without direct contact.
An RFID system comprises three components: an antenna and a transceiver, and a transponder. The antenna uses radio frequency waves to transmit a signal that activates the transponder. When activated the transponder transmits data back to the antenna. The received data is typically used to notify a programmable logic controller that an action should occur. The action could be as simple as raising an access gate. On the other hand the action could be as complicated as interfacing with a database to carry out a monetary transaction. RFID systems use so called active transponders, which transmit a coded signal when it receives a request from a monitoring or control point. The transponder output signal is tracked, so the position of the transponder can be constantly monitored. The input and output frequencies are pre-assigned.
RFID systems use different frequencies. Low-frequency RFID systems use the frequency range from 30 KHz to 50 KHz and have rather short transmission ranges, generally less than six feet. High-frequency RFID systems use the frequency range from 850 MHz to 950 MHz, and from 2.4 GHz to 2.5 GHz. The transmission range of high-frequency RFID can exceed 90 feet.